It has long been known to use heavy machinery to provide precision in finishing metal parts. Lathes and milling machines are examples of machinery that rely on sharp cutting tools to machine metal parts into specific items with close dimensional tolerances.
Typically, lathes are equipped with rotating spindles on which the workpieces are mounted and slide assemblies to mount the cutting tool. As the workpiece is rotated, the sharp cutting tool is advanced, either automatically or manually, into engagement with the workpiece to trim or shave metal from the workpiece until the desired circular dimension is achieved for a particular length of the workpiece. Concentricity of the rotating spindle and alignment between the spindle and the tool mount path is critical.
More recently, specialty lathes have been developed that are dedicated to performing specific tasks where large volume repetitive takes are involved. One example of a dedicated lathe is the brake lathe where the considerable volume brake drums or other brake parts needing restoration justifies a dedicated piece of equipment in an automotive repair business.
Originally, brake lathes were developed to finish the true brake drum surfaces that had been scored or unevenly worn/ Later, brake lathes were developed to restore and true disc brake rotors. The brake drum restoration operation requires the trueing of the inner surface diameter of the drum whereas the restoration of disc brake rotors generally requires refinishing the outer surfaces of the rotor.
There is a significant need in the art for brake lathes which are extremely compact, which are of a simple design for ease of maintenance, which are capable of refinishing brake drums and rotors, and which can be converted quickly from drum to rotor refinishing or from rotor to drum refinishing without the removal or addition of cutting tools. The prior art brake lathes, however, do not have all of the above characteristics.
For example, U.S. Pat. No. 4,455,900 discloses a brake lathe having a rotatable spindle so that its tool slide only needs to move in one direction and the drum or rotor being worked upon can be oriented to the direction of movement of the tool slide. The rotatable spindle design, however, is undesirable as it makes the resulting brake lathe rather large and complex.
Also, U.S. Pat. No. 4,506,570 discloses a lathe apparatus having a pair of substantially identical tool slide modules mounted on the lathe housing at right angles to each other. The shortcoming of this design is that the brake lathe is relatively complex because it has two servomotor driven slide modules, rather than the conventional single slide module.
In addition, U.S. Pat. No. 4,226,146 discloses a portable lathe having a driving device, which is adapted to rotate the brake rotor via a clutch device when the brake rotor is still mounted on the wheel shaft and from which the vehicle wheel has been dismounted. The deficiency of this prior art brake lathe is that it cannot conveniently refinish both drums and rotors as the lathe is intended to refinish primarily brake rotors.